The present invention relates generally to composite materials, and more specifically, to a composite material comprising a ferroelectric material and a ferromagnetic material having improved impedance matching.
Various composite materials are produced comprising a ferroelectric material and a ferromagnetic material. Typically, these composite materials have been designed to dissipate electromagnetic radiation as the electromagnetic radiation passes through the composite material. U.S. Pat. Nos. 5,856,770; 5,601,748; and 5,497,129; each disclose a composite material comprising a ferroelectric material and a ferromagnetic material for dissipating electromagnetic radiation.
These prior art references select the ferroelectric material and ferromagnetic material such that the composite material has a high filtering capability for suppressing electromagnetic interference (EMI). This is accomplished by selecting the ferroelectric material having a favorable dielectric constant (∈) and the ferromagnetic material having a favorable permeability (xcexc). The composite material is then formed by tailoring the amounts of the materials to achieve a xcexc/∈ ratio for the composite material which will dissipate (or reflect) incident electromagnetic radiation in order to reduce electromagnetic interference. In such applications, a high dissipation factor is desired. These composite materials exhibits a loss factor which increases above 1 MHz and therefore the composite material is used to filter EMI at frequencies above 1 MHz. These composite materials disclosed in these patents are not capable of storing, focusing, shaping, or transmitting the electromagnetic radiation without significant energy loss in the material.
However, in applications where the electromagnetic radiation has to be launched into the active material through proper impedance matching with the incident medium, a high dissipation factor is not desirable. It is well known that the velocity of the electromagnetic radiation through a medium is dictated by the square root of the product of xcexc (permeability) and ∈ (permittivity). The greater the value of the product, the slower is the velocity of propagation of the wave through the medium. Moreover, the closer the ratio of xcexc to ∈ is to unity, the better the impedance matching of the circuit is to the impedance of air.
Another composite material, as disclosed in U.S. Pat. Nos. 6,074,971 and 6,063,719, is utilized for impedance matching. The composite material includes a ferroelectric material doped with a magnesium compound. The composite material exhibits a dielectric loss of less than 0.01 at 250 KHz by optimizing the dielectric properties of the composite material at the selected frequency. However, the composite material is formed to exhibit the loss factor at the selected frequency and not over a predetermined frequency range. As the frequency is increased, the dielectric loss of the composite material increases and dissipates electromagnetic radiation. Another disadvantage of the materials disclosed in the ""971 and ""791 patents requires the xcexc/∈ ratio to be near 1. The composite material has a low loss factor (tan xcex4) as measured only by the electronic loss of the ferroelectric material of the composite material.
Accordingly, it would be advantageous to provide a composite material comprising a ferroelectric material and a ferromagnetic material having a loss factor of less than 0.5 for a predetermined frequency range greater than 1 MHz. Furthermore, it would be advantageous to provide the composite material having both the ferroelectric and ferromagnetic material optimized for the predetermined frequency range to produce such a desired result.
The subject invention relates to a composite material comprising a ferroelectric material and a ferromagnetic material combined in amounts sufficient for the composite material to achieve a loss factor of from 0 to about 0.5 for a predetermined frequency range greater than 1 MHz.
The composite material can be formed into a component for use in any application for storing, focusing, shaping, and/or transmitting electromagnetic radiation at a predetermined frequency range. Such components include lenses, prisms, antennas, filters, resonators, and circulators. Each component operates at different frequency ranges and therefore the composite material is optimized for the predetermined frequency range that the component is to be utilized. For example, if the component desired is a resonator operating between 100 MHz and 150 MHz, the composite material is produced to exhibit a loss factor of less than 0.5 for the frequency range between 100 MHz and 150 MHz. In order to achieve the composite material having these properties, both the ferroelectric material and ferromagnetic material losses must be less than 0.5.
Accordingly, the subject invention provides a composite material having a loss factor less than 0.5 for a predetermined frequency range. The composite material also optimizes both the dielectric and magnetic properties of the composite material to achieve the desire result.